A gunman killed three people and wounded two others Thursday morning at a high-rise office building in Cincinnati before he was shot dead by police.

Police responded within seconds to the shooting at the 30-story Fifth Third Center, which sent people running for cover.

Authorities said four officers opened fire, bullets smashing through glass doors as the gunman fell to the floor.

Police said they don’t know what motivated the attack by the 29-year-old gunman.

According to police, the killer used a 9 mm handgun and carried magazines with some 200 rounds of ammunition.

Officials said the gunman, a Cincinnati-area resident since 2015, wasn’t a current or past Fifth Third employee. They said he went into a sandwich shop and possibly other businesses before entering the lobby and opening fire.

Afterward, police swarmed the gunman’s apartment in North Bend, Ohio, about 15 miles west of Cincinnati.